Bitcoin (BTC): how it works, supply and reviews
Layer 1 blockchain
In short
- Type
- Independent layer-1 blockchain with its own peer-to-peer network
- Maximum supply
- 21,000,000 BTC
- Risks and caveats
- Bitcoin transactions are irreversible once confirmed.
- Checked
- 28 October 2026
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Key facts
- Ticker
- BTC
- Category
- Layer 1 blockchain
- Network
- own blockchain
- Launched
- 2009-01
- Mining algorithm
- SHA-256
- Official site
- bitcoin.org
- Whitepaper
- bitcoin.org/bitcoin.pdf
- Source code
- github.com/bitcoin/bitcoin
Data: CoinGecko, 2026-10-27. Only projects that still trade with meaningful volume are listed.
What is Bitcoin
Bitcoin is a peer-to-peer electronic cash system that lets payments move directly between people without a bank or other central authority. Transactions are recorded on a public blockchain secured by proof-of-work mining, and BTC is the network's native currency.
Network and consensus
| Parameter | Details |
|---|---|
| Type | Independent layer-1 blockchain with its own peer-to-peer network |
| Consensus | Proof of work (mining); the longest valid chain is followed |
| Launched | Genesis block timestamped 3 January 2009 |
| Block time | About 10 minutes on average; mining difficulty adjusts automatically to keep this pace |
| Smart contracts | Limited scripting: outputs are locked by scripts such as multi-signature conditions |
Supply and issuance
| Parameter | Details |
|---|---|
| Maximum supply | 21,000,000 BTC |
| Issuance | New BTC are paid to miners in each block at a fixed, decreasing rate until issuance stops |
| Halving | The block subsidy halves every 210,000 blocks (roughly every four years) |
| Initial distribution | No pre-sale: the first block paid a 50 BTC subsidy, and all BTC enter circulation through mining |
What BTC is used for
- Sending and receiving payments directly between users
- Paying transaction fees to miners
- Rewarding miners, together with newly issued BTC, for securing the network
Who develops and governs Bitcoin
- Founders
- Created by the pseudonymous Satoshi Nakamoto, who left the project in late 2010
- Governance
- No company or foundation controls it; changes are proposed publicly as BIPs and take effect only if users, miners and node operators adopt them
- Developer
- Bitcoin Core, an open-source project descended from the original client, is the main reference software
- Open source
- Yes; Bitcoin Core is released under the MIT license
History
| Date | Event |
|---|---|
| 3 January 2009 | Genesis block created with the embedded headline "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks". |
| 2009 | Satoshi Nakamoto publishes the first Bitcoin specification and proof of concept on a cryptography mailing list. |
| 2010 | Satoshi Nakamoto leaves the project; development continues through an open community of contributors. |
Security and audits
- Bitcoin Core publishes a vulnerability disclosure policy; issues are reported to security@bitcoincore.org and assigned a severity class.
- Security flaws have been found and fixed in software implementations over time; the protocol rules themselves have run since 2009.
- Losses on exchanges and businesses did not involve the Bitcoin protocol itself; the most common risk is user error, such as lost or stolen wallet keys.
Risks and caveats
- Bitcoin transactions are irreversible once confirmed.
- Whoever holds the private keys controls the funds; lost or stolen keys mean lost coins.
- Legal treatment differs by country: some jurisdictions restrict or ban its use, and rules continue to change.
- Quantum computers able to break Bitcoin's cryptography do not exist yet; the protocol would need an upgrade if that changed.
Official links
- Website: bitcoin.org/en
- Whitepaper: bitcoin.org/bitcoin.pdf
- Source code: github.com/bitcoin/bitcoin
- Docs: developer.bitcoin.org/devguide/block_chain.html
Questions and answers
What is Bitcoin?
Bitcoin is a peer-to-peer electronic cash system that runs without a bank or central authority. BTC is its native currency.
Who created Bitcoin?
Bitcoin was created by the pseudonymous Satoshi Nakamoto, who published the first specification and proof of concept in 2009 and left the project in late 2010.
What is the maximum supply of Bitcoin?
Only 21 million BTC will ever be created. The block subsidy halves every 210,000 blocks until issuance stops.
How does Bitcoin reach consensus?
Miners compete to produce proof of work for each block, and difficulty adjusts so a block is found about every 10 minutes on average.
Who controls Bitcoin?
No single person or group. Protocol changes are proposed publicly and take effect only if users, miners and node operators choose to adopt them.
Sources
- CoinGecko — Bitcoin
- Bitcoin: A Peer-to-Peer Electronic Cash System (whitepaper)
- Bitcoin.org — Frequently Asked Questions
- Bitcoin.org — home page
- Bitcoin Core — About
- Bitcoin Core — Security advisories
- Bitcoin Core source — chainparams.cpp
- Bitcoin Developer Glossary
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